HOT FLASHES: Rock faves U-2 will have a new album out this spring, with a U.S. tour to follow. No official announcement has been made yet, but U-2 fans should keep April 15 through 18 free, which is when the band is expected to arrive here. . . . Deirdre( O'Donoughue, whose popular "SNAP" program was canceled by KCRW-FM late last year, will be playing the future hits again starting tonight on KMET-FM (where she already does a Sunday morning Beatles program). The weekly new music show will air Sundays from 11 p.m. to midnight. . . . And Performance, the new dance club based downtown at the Variety Arts Center, will host "The Incredibly Strange Film Festival" this Saturday, featuring such Herschell Gordon Lewis cult-faves as "Blood Feast," "She Devils on Wheels" and "2000 Maniacs." The films will be followed by an 11 p.m. "Maniac's Dance Party."